The most common cause of first-trimester miscarriage is completely unpreventable: fetal chromosomal abnormality. This is the result of errors in the cell division process inherent to the embryo.
In contrast, a miscarriage that occurs in the second trimester of pregnancy is usually related to an issue in the mother’s reproductive system.
Here are a few causes of miscarriage that are directly associated with the mother:
1. Hormonal factors: These include any illness that is characterized as an imbalance in the mother’s hormone levels. Examples of these include Cushing’s syndrome, thyroid disease and polycystic ovary syndrome (PCOS).
2. Chronic illness: Conditions such as diabetes can increase the risks of miscarriage and birth defects. High blood pressure, lupus and an underactive or overactive thyroid can also cause problems.
3. Acute Infection: Certain infections that put the mother at risk can cross the placental barrier and infect the fetus. In developing countries, malaria is a common cause of miscarriages. Malaria can also cause preterm delivery, low birth weight and stillbirth. In developing countries, common infections include pneumonia, rubella, and sexually transmitted illnesses such as chlamydia, gonorrhea and herpes.
4. Reproductive anatomy abnormalities: Some women may have a septum (i.e. wall) that separates the uterus into sections. Uterine septa usually have poor blood supply, thus the placenta will have difficulty developing, resulting in undernourishment of the fetus. Lack of muscle tone at the cervix (the opening of the uterus into the vaginal canal) also makes a miscarriage more likely. Uterine fibroids, despite their benign, non-cancerous nature, can block the embryo’s implantation and blood supply and lead to miscarriage.
5. Lifestyle factors: Smoking has been shown to increase the risk of miscarriage. Alcohol consumption during pregnancy is also harmful. For a mother who drinks more than 30 ounces of alcohol a month, her risk of miscarriage is doubled. It is important to note that it has not been determined how much alcohol is safe during a pregnancy, and most American doctors recommend complete abstinence. Excessive amounts of caffeine, usually 200 mg or more, has also been linked with miscarriage. Diet also plays an important role in gestational health. Malnourished mothers also have an increased chance of miscarriage, and women who are severely underweight are not healthy enough to get pregnant.
6. Trauma: It is important for pregnant women to avoid putting their bodies at risk for physical injury. Most doctors advise women who have an active lifestyle to adjust their physically demanding routines. Trauma greatly increases the risk of miscarriage. This includes surgeries to the lower pelvic area, or invasive procedures that could involve the uterus or endanger the developing fetus. These types of procedures are usually avoided or delayed until after delivery, but if they are absolutely necessary, they are performed only in emergency situations.